1. Field of the Invention
This invention relates to motor vehicle axle lift suspensions. More particularly, the invention relates to a lock mechanism for mechanically latching an axle in a lifted position.
2. Scope of the Prior Art
Several types of vehicles, including semitrailer truck vehicles and the like, have multiple sets of axle/wheel assemblies arranged in tandem so as to adequately support relatively heavy loads. To adjust the load provided by these tandem assemblies, it is known to employ suspension systems utilizing adjustably pressurized air springs and the like. It is sometimes desirable for various purposes to disengage one or more axle/wheel assemblies from ground contact. For example, when the vehicle is carrying a relatively light load, disengagement of the axle/wheel assembly will reduce tire wear. In some systems, such as a bimodal vehicle, wherein the vehicle can be adapted for both highway and railroad use, it is desirable to retract the highway axle/wheel assembly from ground contact to permit the introduction of a rail bogie for use in normal rail service. In either case, devices commonly referred to as axle lift mechanisms can be employed. For suspension systems that utilize air springs, an axle lift mechanism will typically lift the entire suspension.
Prior lift mechanisms employ a variety of devices to achieve disengagement. For example, stressed mechanical springs can be interposed directly between a vehicle frame and the axle. A chain and link mechanism can be employed such as that disclosed in U.S. Pat. No. 3,771,812, issued Nov. 13, 1973. Other lift mechanisms employ cams, levers, and springs such a those disclosed in U.S. Pat. No. 4,634,141, issued Jan. 6, 1987. Still other lift axle suspensions utilize air springs coupled with links such as the mechanism disclosed in U.S. Pat. No. 4,300,787, issued Nov. 17, 1981.
It has been found advantageous to provide an improved means for securing an axle/wheel assembly in a lifted position.